In their aim to reach the deepest parts of the 5 oceans in the world, Victor Vescovo, a diver from the Five Deeps Expedition, along with his team, was exploring 23,596 feet deep in the Indian Ocean, which is believed to be the ocean’s deepest part, when they spotted what seemed to be a new species of jellyfish or an unknown sea squirt.

The Five Deeps team captured footage of the creature, from DSV Limiting Factor, the world’s deepest diving, currently operational submarine, calling it an “extraordinary gelatinous animal” which “does not resemble anything seen before.”

The creature is believed to be a tunicate, particularly a stalked ascidean, also known as a sea squirt.

“Amongst many other rare and unique observations, the stalked Ascidean was a really significant moment,” Alan Jamieson, the expedition’s chief scientist, said in a statement. “It is not often we see something that is so extraordinary that it leaves us speechless. At this point we are not entirely sure what species it was, but we will find out in due course.”

Noah Webster's spelling reform is responsible for the meter spelling. At this point is somewhere between silly to ignorant to pretend dialects don't exist. If you want to be a stickler for not changing loan words, you could use metro from before the French changed it. I find it more useful to stick to official style guides for publications than risk annoying editors, so that means meter in American English and many Germanic languages.